* validation of client moved into its own method and tested
* public clients have different validation - must have no redirect URIs
and must have a clientName set
The Client object on its own doesn't fully express everything about a
single client, and so when loading clients from a static configuration
it's not enough to just (de)serialize clients.
To that end, LoadableClient contains the full representation of a client
and associated entities.
The DB implementation expects secrets to be base64 encoded blobs.
Because of this a bunch of tests broke moving to sqlite.
A lot of this commit is fixing those tests.
